Method for making thin film transistor

ABSTRACT

A method of making thin film transistor including: forming a gate electrode, forming a gate insulating layer on the gate electrode; locating a semiconductor layer on the gate insulating layer; placing stripe-shaped masks on the semiconductor layer, wherein the thickness of the stripe-shaped masks is H, the spacing distance between the stripe-shaped masks is L; depositing a first conductive film layer along a first direction, the thickness of the first conductive film layer is D, a first angle between the first direction and a direction along the thickness of the stripe-shaped masks is θ1, θ1&lt;tan−1(L/H); depositing a second conductive film layer along a second direction, a second angle between the second direction and the direction along the thickness of the stripe-shaped masks is θ2, θ2&lt;tan−1[L/(H+D)], 0&lt;Htanθ1+(H+D)tanθ2−L&lt;10 nm, the first conductive film layer forms a source electrode, the second conductive film layer forms a drain electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to applications entitled, “METHOD FOR MAKING NANOSCALE CHANNELS”, U.S. patent application Ser. No. 16/008,211, filed on Jun. 14, 2018, “METHOD FOR MAKING NANOSTRUCTURES”, U.S. patent application Ser. No. 16/008,216, filed on Jun. 14, 2018, and “METHOD FOR MAKING NANOSCALE BELTS”, U.S. patent application Ser. No. 16/008,205, filed on Jun. 14, 2018.

FIELD

The subject matter herein generally relates to a method for making thin film transistor.

BACKGROUND

Currently, when preparing nanostructures, the minimum processing size of the nanostructures is mainly determined by the performance of the processing devices. For certain dimensions, especially those less than about 10 nanometers, the majority of processing devices have difficulty not only preparing the nanostructures, but also forms controlling costs, consistencies, yields, and other processing parameters.

Methods for making less than about 10 nanometers structures include evaporation stripping method and etching method. These methods require small-sized patterned photoresist layers used as a mask to prepare small dimension structures such as fine groove structures. However, it is difficult to create the small-sized photoresist layers. If the photoresist layer is too thick, it is difficult to stand up and easy to collapse. If the photoresist layer is too thin, it is difficult to transfer the photoresist layer. Also when the photoresist is removed by peeling or etching, the photoresist has a small amount of residue which cause the small dimension structures to be inaccurate.

Thus, there is room for improvement within the art.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. Implementations of the present technology will be described, by way of example only, with reference to the attached figures

FIG. 1 is a flow chart of an embodiment of a method for making nanoscale channels.

FIG. 2 is a schematic view of an embodiment of a strip mask after development.

FIG. 3 is a Scanning Electron Microscope (SEM) image of nanoscale channels.

FIG. 4 is a flow chart of an embodiment of a method for depositing a first film layer and a second film layer.

FIG. 5 is a flow chart of an embodiment of a method for depositing a first film layer and a second film layer.

FIG. 6 is a flow chart of an embodiment of a method for making a thin film transistor with nanoscale channels.

FIG. 7 is a flow chart of an embodiment of a method for making nanostructures.

FIG. 8 is a flow chart of an embodiment of a method for making nanoscale belts.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. The drawings are not necessarily to scale, and the proportions of certain parts may be exaggerated to better illustrate details and features. The description is not to be considered as limiting the scope of the embodiments described herein.

Several definitions that apply throughout this disclosure will now be presented.

The connection can be such that the objects are permanently connected or releasably connected. The term “substantially” is defined to be essentially conforming to the particular dimension, shape, or other feature that the term modifies, such that the component need not be exact. The term “comprising” means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in a so-described combination, group, series, and the like. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean “at least one.”

In FIG. 1 and FIG. 2, an embodiment of a method of making nanoscale channels may comprise at least the following steps:

-   -   S11, providing a substrate 10, locating a photoresist mask layer         11 on the substrate, the thickness of the photoresist mask layer         11 equals H;     -   S12, forming a patterned mask layer 12 by exposing and         developing the photoresist mask layer 11, the patterned mask         layer 12 comprises a plurality of parallel and spaced stripe         masks 121, the spacing between adjacent stripe masks 121 equals         L, a top surface of the patterned mask layer 12 the substrate 10         defines a first area I, a side surface of the patterned mask         layer 12 defines a second area II, a surface of the substrate 10         exposed between adjacent stripe masks 121 defines a third area         III;     -   S13, rotating the substrate 10 with an extending direction of         the stripe masks 121 as a rotation axis, a first angle between         the substrate 10 and the horizontal direction equals θ₁,         θ₁<tan⁻¹(L/H), depositing a first thin film layer 13 on the         substrate 10 in a vertical direction, the thickness of the first         thin film layer 13 equals D;     -   S14, rotating the substrate 10 back to the horizontal direction,         continuing to rotate the substrate 10 to obtain a second angle,         the second angle between the substrate 10 and the horizontal         direction equals θ₂, θ₂<tan⁻¹[L/(H+D)], depositing a second thin         film layer 14 on the substrate 10 in the vertical direction,         0<Htanθ₁+(H+D)tanθ₂−L<10 nm, an interval area between the first         thin film layer 13 and the second thin film layer 14 in the         third area III is a nanoscale channel.

In step S11, the material of the substrate 10 can be insulating materials such as silica or silicon nitride. The material of the substrate 10 can also be conductive materials such as gold, aluminum, nickel, chromium, or copper. Also the material of the substrate 10 can be semiconductor materials such as silicon, gallium nitride, or gallium arsenide. In one embodiment, the material of the substrate 10 is a silicon wafer.

The photoresist mask layer 11 plays a role in shielding. The material of the photoresist mask layer 11 is photoresist. The type of the photoresist mask layer 11 can be negative or positive. The photoresist mask layer 11 can be electron beam photoresist or ultraviolet photoresist, such as S9912, SU8, poly methyl methacrylate (PMMA), ZEP, hydrogen silsesquioxane (HSQ). The photoresist mask layer 11 can be directly coated on the substrate 10 by spin coating. The thickness of H can be adjusted according to need. The thickness of H is in a range of 200 nanometers to 400 nanometers. The thickness of H can be in a range of 300 nanometers to 400 nanometers. In one embodiment, the material of the photoresist mask layer 11 is HSQ, and the thickness of H is 400 nanometers.

In step S12, the photoresist mask layer 11 is exposed by using a pattern as an exposure pattern. The shape and size of the pattern can be set according to need. The exposure intensity and exposure time can be adjusted according to the thickness and material of the photoresist mask layer 11. In one embodiment, the photoresist mask layer 11 is exposed by electron beam. After exposed, the photoresist mask layer 11 is placed into a developer to obtain the patterned mask layer 12. The exposed part of the photoresist mask layer 11 is removed by the developer. The first area I is the top surface of the patterned mask layer 12, and the first area I is also the top surface of the stripe masks 121. The second area II is the side surface of the patterned mask layer 12, and the side surface is perpendicular to the substrate 10. The second area II is produced after removing the exposed photoresist. The third area III is the exposed surface of the substrate 10 between adjacent stripe masks 121. The third area III is produced after removing the exposed photoresist to expose a portion of the substrate 10. In one embodiment, the developer is tetramethylammonium hydroxide (TMAH) solution, and the developing time is 90 s. The plurality of stripe masks 121 can be arranged in a row, or can also be arranged in multiple rows. The spacing of adjacent stripe masks 121 in each row equals L. The spacing of L is in a range of 200 nanometers to 1000 nanometers. The spacing of L can also be in a range of 400 nanometers to 500 nanometers. In one embodiment, the spacing of L is 400 nanometers.

In step S13, the plurality of stripe masks 121 extend in the same direction. The extending direction of stripe masks 121 forms the rotation axis to rotate the substrate 10. Before rotating the substrate 10, the substrate 10 is placed horizontally. After rotating the substrate 10, the first angle between the substrate 10 and the horizontal direction is θ₁, and θ₁<tan⁻¹(L/H). A thickness direction of the stripe masks 121 is perpendicular to the surface of the substrate 10, and a direction of depositing the first thin film layer 13 is the vertical direction, so the angle between the thickness direction of the stripe masks 121 and the direction of depositing the first thin film layer 13 is also θ₁. The range of θ₁ is θ₁≤45 degrees. In one embodiment, the angle θ₁ is 30 degrees. When depositing the first thin film layer 13 in the vertical direction, the first thin film layer 13 can not cover the entire surface of the substrate 10 and the entire surface of the stripe masks 121. A part surface of the substrate 10 and a part surface of the stripe masks 121 can not be deposited by the first thin film layer 13 due to the obstruction of the stripe masks 121. The position of the surface of the substrate 10 without the first thin film layer 13 can be adjusted by adjust the first angle θ₁, the thickness of the stripe masks 121, or the spacing L.

The material of the first thin film layer 13 can be metal materials such as gold, nickel, titanium, iron, aluminum. The material of the first thin film layer 13 can also be nonmetallic materials such as alumina, magnesium oxide, zinc oxide, hafnium oxide, and silica. The material of the first thin film layer 13 is not limited to the above as long as the material used can be formed into a film. The first thin film layer 13 can be deposited by magnetron sputtering, electron beam evaporation, or the like. The thickness of D is less than 40 nanometers. In one embodiment, the first thin film layer 13 is formed by electron beam evaporation, the material of the first thin film layer 13 is aluminum, and the thickness of D is 30 nanometers.

In step S14, the substrate 10 is rotated back to the horizontal direction by selecting a clockwise or counterclockwise rotation according to need. After the substrate 10 being rotated back to the horizontal direction, the substrate 10 continues to be rotated to obtain the second angle θ₂ between the substrate 10 and the horizontal direction, θ₂<tan⁻¹[L/(H+D)]. Similarly, the angle between the thickness direction of the stripe masks 121 and the direction of depositing the second thin film layer 14 is also θ₂. The range of θ₂ is θ₂≤45 degrees. In one embodiment, the angle θ₂ is 30 degrees. When depositing the second thin film layer 14 in the vertical direction, the second thin film layer 14 can not cover the entire surface of the substrate 10 and the entire surface of the stripe masks 121. A partial surface of the substrate 10 and a partial surface of the stripe masks 121 can not be deposited by the second thin film layer 14 due to the obstruction of the stripe masks 121. When depositing the first thin film layer 13 and the second thin film layer 14, the parameters H, θ₁, θ₂, D, and L should satisfy 0<Htanθ₁+(H+D)tanθ₂−L<10 nm, so that the first thin film layer 13 and the second thin film layer 14 are spaced from each other on the substrate 10, and the spacing is in a nanometer range. The spacing is less than 20 nanometers. The spacing can be less than 10 nanometers. In one embodiment, the spacing is 9.67 nanometers. This is shown in FIG. 3 an SEM image showing nanoscale channels.

The material of the second thin film layer 14 can be metal materials such as gold, nickel, titanium, iron, aluminum. The material of the second thin film layer 14 can also be nonmetallic materials such as alumina, magnesium oxide, zinc oxide, hafnium oxide, and silica. The material of the second thin film layer 14 is not limited to the above as long as the material used can be formed into a film. The material of the second thin film layer 14 and the material of the first thin film layer 13 can be the same or different. The second thin film layer 14 can be deposited by magnetron sputtering, electron beam evaporation, or the like. The thickness of the second thin film layer 14 can be adjusted according to need. In one embodiment, the second thin film layer 14 is formed by electron beam evaporation, the material of the second thin film layer 14 is aluminum, and the thickness of the second thin film layer 14 is 30 nanometers.

In the vertical deposition process, the first thin film layer 13 and the second thin film layer 14 can be deposited downwardly as in FIG. 1, and the first thin film layer 13 and the second thin film layer 14 can also be deposited upwardly as in FIG. 4. When the surface of the substrate having the stripe masks 121 is inverted to be downward, the first thin film layer 13 and the second thin film layer 14 are deposited on the substrate 10 and the stripe masks 121 upwardly.

The method of depositing the first thin film layer 13 and the second thin film layer 14 is not limited above as long as the parameters H, θ₁, θ₂, D, and L satisfy 0<Htanθ₁+(H+D)tanθ₂−L<10 nm. The deposition direction should be adjusted in a plane perpendicular to the extending direction of the stripe masks 121. Referring to FIG. 5, when the substrate 10 is fixed horizontally, the first thin film layer 13 and the second thin film layer 14 can be deposited by adjusting the angle between the deposition direction and the thickness direction of the stripe masks 121.

The advantages of the method of making nanoscale channels are described below. The nanoscale channels can be formed by a lateral deposition method. In the deposition process, the nanoscale channels can be formed by adjusting the parameters of deposition without etching and stripping. The substrate can not be damaged. The position of the nanoscale channels can be controlled precisely by the lateral deposition method, and the nanoscale channels can be prepared at any position. The width of the nanoscale channels can be adjusted according to need. A material deposited on one side of the nanoscale channel can be different from the material deposited on the other side of the nanoscale channel.

Referring to FIG. 6, an embodiment of a method of making a thin film transistor 20 with nanoscale channels comprises:

-   -   S21, providing a gate electrode 22 on a substrate 21, forming a         gate insulating layer 23 on a surface of the gate electrode 22;     -   S22, locating a semiconductor layer 24 on the gate insulating         layer 23;     -   S23, placing a first stripe mask 122 and a second stripe mask         123 on the semiconductor layer 24, wherein the first stripe mask         122 and the second stripe mask 123 are parallel and spaced from         each other, the thickness of the first stripe mask 122 and the         thickness of the second stripe mask 123 are both set to H, the         spacing between the first stripe mask 122 and the second stripe         mask 123 equals L;     -   S24, rotating the semiconductor layer 24 with an extending         direction of the first stripe mask 122 as a rotation axis, a         first angle between the semiconductor layer 24 and the         horizontal direction equals θ₁, θ₁<tan⁻¹(L/H), depositing a         first conductive film layer 25 on the semiconductor layer 24 in         the vertical direction, the thickness of the first conductive         film layer 25 equals D;     -   S25, rotating the semiconductor layer 24 back to the horizontal         direction, continuing to rotate the semiconductor layer 24 to         obtain a second angle, the second angle between the         semiconductor layer 24 and the horizontal direction equals θ₂,         θ₂<tan⁻¹[L/(H+D)], depositing a second conductive film layer 26         on the semiconductor layer 24 in the vertical direction,         0<Htanθ₁+(H+D)tanθ₂−L<10 nm, an interval area between the first         conductive film layer 25 and the second conductive film layer 26         is a nanoscale channel, the first conductive film layer 25 forms         a source electrode 27, and the second conductive film layer 26         forms a drain electrode 28.

In step S21, the material of the gate electrode 22 is a conductive material. The conductive material can be metal, indium tin oxide, arsenic trioxide, conductive silver glue, conductive polymers, or conductive carbon nanotubes. The metal materials can be aluminum, copper, tungsten, molybdenum, gold, titanium, palladium or any combination of alloys.

The material of the gate insulating layer 23 can be hard materials such as alumina, hafnium oxide, silicon nitride, or silicon oxide. The material of the gate insulating layer 23 can also be flexible materials such as benzocyclobutene (BCB), polyester, or acrylic resin.

The gate insulating layer 23 can be deposited on the gate electrode 22 by a magnetron sputtering method or a electron beam deposition method. In one embodiment, the gate insulating layer 23 is deposited by electron beam deposition, and the material of the gate insulating layer 23 is alumina.

In step S22, the material of the semiconductor layer 24 can be gallium arsenide, gallium phosphide, gallium nitride, silicon carbide, germanium silicide, silicon, germanium, carbon nanotubes, graphene, or molybdenum sulfide. The method of forming the semiconductor layer 24 can be tiling method, epitaxial growth method, or vapor deposition method. When the semiconductor layer 24 is a carbon nanotube layer, a graphene layer or a molybdenum sulfide layer, the semiconductor layer 24 can be transferred to the gate insulating layer 23 by a photoresist layer. The thickness of the semiconductor layer 24 can be adjusted according to need. The thickness of the semiconductor layer 24 should be less than 10 nanometers. In one embodiment, the thickness of the semiconductor layer 24 is 2 nanometers.

In steps S23 to S25, the method of making nanoscale channels is similar to the method of making nanoscale channels of FIG. 1 except that a first conductive film layer 25 and a second conductive film layer 26 are directly deposited on the semiconductor layer 24 to form a thin film transistor having a nanoscale channel. The first area I is the top surfaces of the first stripe mask 122 and the second stripe mask 123. The second area II is the side surfaces of the first stripe mask 122 and the second stripe mask 123, and the side surfaces are perpendicular to the semiconductor layer 24. The third area III is the exposed surface of the semiconductor layer 24 between the first stripe mask 122 and the second stripe mask 123. The material of the first conductive film layer 25 can be aluminum, nickel, gold, titanium, iron. The material of the second conductive film layer 26 can be aluminum, nickel, gold, titanium, iron. The first conductive film layer 25 located on the semiconductor layer 24 forms the source electrode 27, and the second conductive film layer 26 located on the semiconductor layer 24 forms the drain electrode 28.

Furthermore, the source electrode 27 and the drain electrode 28 can also be formed before making the gate electrode 22. Thus, a top gate type thin film transistor can be formed.

The method of making the thin film transistor 20 further includes a step of removing the first stripe mask 122 and the second stripe mask 123. The first stripe mask 122 and the second stripe mask 123 can be removed by chemical reagent. For example, the structure obtained in step S25 can be placed in an acetone solution to remove the first stripe mask 122 and the second stripe mask 123. When the first conductive film layer 25 and the second conductive film layer 26 are not free-standing structures, the first conductive film layer 25 located on the first area I and the second area II can be removed due to loss of support, and the second conductive film layer 26 located on the first area I and the second area II can also be removed due to loss of support. After removing the first stripe mask 122 and the second stripe mask 123, the first conductive film layer 25 located on the semiconductor layer 24 forms the source electrode 27, and the second conductive film layer 26 located on the semiconductor layer 24 forms the drain electrode 28. When the first conductive film layer 25 and the second conductive film layer 26 are free-standing structures, the first conductive film layer 25 located on the first area I and the second area II can be removed by dry etching, and the second conductive film layer 26 located on the first area I and the second area II can also be removed by dry etching. The term “free-standing structure” means that the structure can sustain the weight of itself when hoisted by a portion thereof without any significant damage to its structural integrity.

Referring to FIG. 7, an embodiment of a method of making nanoscale microstructure comprises:

-   -   S31, providing a substrate 30, locating a photoresist mask layer         31 on the substrate, the thickness of the photoresist mask layer         31 equals H;     -   S32, forming a patterned mask layer 32 by exposing and         developing the photoresist mask layer 31, the patterned mask         layer 32 comprises a plurality of parallel and spaced stripe         masks 321, the spacing between adjacent stripe masks 321 equals         L, a top surface of the patterned mask layer 32 defines a first         area I, a side surface of the patterned mask layer 32 defines a         second area II, a surface of the substrate 30 exposed between         adjacent stripe masks 321 defines a third area III;     -   S33, rotating the substrate 30 with an extending direction of         the stripe masks 321 as a rotation axis, a first angle between         the substrate 30 and the horizontal direction equals θ₁,         θ₁<tan⁻¹(L/H), depositing a first thin film layer 33 on the         substrate 30 in the vertical direction, the thickness of the         first thin film layer 33 equals D;     -   S34, rotating the substrate 30 back to the horizontal direction,         continuing to rotate the substrate 30 to obtain a second angle,         the second angle between the substrate 30 and the horizontal         direction equals θ₂, θ₂<tan⁻¹[L/(H+D)], depositing a second thin         film layer 34 on the substrate 30 in the vertical direction,         0<L−Htanθ₁−(H+D)tanθ₂<10 nm, the first thin film layer 33         partially overlaps with the second thin film layer 34 to form an         overlapping structure and a non-overlapping structure;     -   S35, removing the plurality of stripe masks 321;     -   S36, dry etching the first thin film layer 33 and the second         thin film layer 34 to obtain a nanoscale microstructure 35,         wherein the width of the nanoscale microstructure 35 equals the         width of the overlapping structure, and the non-overlapping         structure is etched away.

The steps S31-S33 are the same as the steps S11-S13 of FIG. 1, the stripe masks 321 can be formed on the substrate 30, and the first thin film layer 33 can be deposited on the substrate 30 and the stripe masks 321.

In step S34, the method of depositing the second thin film layer 34 is similar to the method of depositing the second thin film layer 14 except that the second thin film layer 34 partially overlaps the first thin film layer 33. The width of the overlapping structure is in the nanometer scale. When depositing the first thin film layer 33 and the second thin film layer 34, the parameters H, θ₁, θ₂, D, and L should satisfy 0<L−Htanθ₁−(H+D)tanθ₂<10 nm, so that the second thin film layer 34 partially overlaps the first thin film layer 33 on the substrate 30, and the width of the overlapping structure is in the nanometer scale.

In step S35, the stripe masks 321 can be removed by chemical reagent. For example, the structure formed in step S34 can be placed in an acetone solution to remove the stripe masks 321. When the first film layer 33 and the second film layer 34 are not free-standing structures, the first film layer 33 located on the first area I and the second area II can be removed due to loss of support, and the second film layer 34 located on the first area I and the second area II can also be removed due to loss of support. Thus, only the first film layer 33 and the second film layer 34 located on the third area III are retained. When the first film layer 33 and the second film layer 34 are free-standing structures, the first film layer 33 located on the first area I, the second area II and the third area III are all remained, and the second film layer 34 located on the first area I, the second area II and the third area III all remain. The term “free-standing structure” means that the structure can sustain the weight of itself when hoisted by a portion thereof without any significant damage to its structural integrity.

In step S36, the dry etching can be plasma etching or reactive ion etching (RIE). In one embodiment, the dry etching is performed by applying plasma energy on the entire or partial surface of the first film layer 33 and the second film layer 34 via a plasma device. The plasma gas can be an inert gas and/or etching gases, such as argon (Ar), helium (He), chlorine (Cl₂), hydrogen (H₂), oxygen (O₂), fluorocarbon (CF₄), ammonia (NH₃), or air.

When the first film layer 33 and the second film layer 34 are still integrated structures after removing the stripe masks 321, the first film layer 33 located on the first area I and the second area II can be removed by dry etching, and the second film layer 34 located on the first area I and the second area II can also be removed by dry etching. When dry etching the first thin film layer 33 and the second thin film layer 34 located on the third area III, the first thin film layer 33 and the second thin film layer 34 are etched at the same time. Since the thickness of the overlapping structure is greater than the thickness of the first thin film layer 33, and is greater than the thickness of the second thin film layer 34, and the etching rate of the first thin film layer 33 is the same as the etching rate of the second thin film layer 34, the overlapping structure still remains after the non-overlapping structure of the first thin film layer 33 and the second thin film layer 34 being etched away. The overlapping structure remained is the nanoscale microstructure. Thus, the width of the nanoscale microstructure is the same as the width of the overlapping structure. In the process of etching, no mask is provided to make the nanoscale microstructure.

Furthermore, the first thin film layer 33 and the second thin film layer 34 can be etched before removing the stripe masks 321. the first thin film layer 33 and the second thin film layer 34 located on the first area I can be etched firstly, then the first thin film layer 33 and the second thin film layer 34 located on the second area II and the third area III continue to be etched.

The advantages of the method of making nanostructures according to the processes described herein are described below. The nanostructures can be formed by a lateral deposition method. During the deposition process, the nanostructures can be formed by adjusting the deposition parameters. The nanostructure positioning can be controlled precisely by the lateral deposition method, and the nanostructures can be prepared at any position. The width of the nanostructures can be adjusted according to need.

Referring to FIG. 8, an embodiment of a method of making nanoscale belts comprises:

-   -   S41, providing a semiconductor thin film 42 on a substrate 41,         placing a plurality of parallel and spaced stripe masks 421 on         the semiconductor thin film 42, wherein the thickness of the         stripe masks 421 equals H, the spacing between adjacent stripe         masks 421 equals L;     -   S42, rotating the semiconductor thin film 42 with an extending         direction of the stripe masks 421 as a rotation axis, a first         angle between the semiconductor thin film 42 and the horizontal         direction equals θ₁, θ₁<tan⁻¹(L/H), depositing a first thin film         layer 43 on the semiconductor thin film 42 in the vertical         direction, the thickness of the first thin film layer 43 equals         D;     -   S43, rotating the semiconductor thin film 42 back to the         horizontal direction, continuing to rotate the semiconductor         thin film 42 to obtain a second angle, the second angle between         the semiconductor thin film 42 and the horizontal direction         equals θ₂, θ₂<tan⁻¹[L/(H+D)], depositing a second thin film         layer 44 on the semiconductor thin film 42 in the vertical         direction, 0<L−Htanθ₁−(H+D)tanθ₂<10 nm, the first thin film         layer 43 partially overlaps with the second thin film layer 44         to form an overlapping structure and a non-overlapping         structure;     -   S44, removing the plurality of stripe masks 421;     -   S45, dry etching the first thin film layer 43 and the second         thin film layer 44 to obtain a nanostructure 45;     -   S46, etching the semiconductor thin film 42 using the         nanostructure 45 as a mask to obtain a nanoscale belt 46.

In step S41, the material of the semiconductor thin film 42 is a two-dimensional material such as graphene, molybdenum sulfide and the like. The semiconductor thin film 42 are formed on the substrate 41 by tiling method, vapor deposition. The thickness of the semiconductor thin film 42 can be adjusted according to need. In one embodiment, the material of the semiconductor thin film 42 is graphene.

The steps S42-S45 are the same as the steps S33-S36 of FIG. 7. The nanostructure 45 can be used as the mask to make the nanoscale belt 46.

A first area I is the top surfaces of the stripe masks 421. The second area II is the side surfaces of the stripe masks 421, and the side surfaces are perpendicular to the semiconductor thin film 42. The third area III is the exposed surface of the semiconductor thin film 42 between the adjacent stripe masks 421.

In step S46, the semiconductor thin film 42 includes a covered portion and a non-covered portion, the covered portion is covered by the nanostructure 45. when the non-covered portion of the semiconductor thin film 42 is etched, the nanostructure 45 can further be etched. Since the nanostructure 45 forms the mask, so the nanostructure 45 should not be completely etched away before the non-covered portion of the semiconductor thin film 42 being etched away.

After etching away the non-covered portion of the semiconductor thin film 42, the nanostructure 45 is not completely etched away. Thus, the nanostructure 45 remained can further be removed by wet etching. In one embodiment, the nanostructure 45 remained is removed by hydrochloric acid solution.

The embodiments shown and described above are only examples. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be formed in the detail, including in matters of shape, size, and arrangement of the parts within the principles of the present disclosure, up to and including the full extent established by the broad general meaning of the terms used in the claims.

Depending on the embodiment, certain of the steps of methods described may be removed, others may be added, and the sequence of steps may be altered. The description and the claims drawn to a method may comprise some indication in reference to certain steps. However, the indication used is only to be viewed for identification purposes and not as a suggestion for ordering the steps. 

What is claimed is:
 1. A method of making thin film transistor, comprising: forming a gate electrode on a substrate; forming a gate insulating layer on the gate electrode; forming a semiconductor layer on the gate insulating layer; forming a first stripe-shaped mask and a second stripe-shaped mask on the semiconductor layer, wherein the first stripe-shaped mask and the second stripe-shaped mask are parallel, spaced from each other and have a same thickness, a first thickness of the first stripe-shaped mask and the second stripe-shaped mask equals H, a spacing distance between the first stripe-shaped mask and the second stripe-shaped mask equals L, top surfaces of the first stripe-shaped mask and the second stripe-shaped mask away from the semiconductor layer defines a first area I, side surfaces of the first stripe-shaped mask and the second stripe-shaped mask defines a second area II, an exposed surface of the semiconductor layer between the first stripe-shaped mask and the second stripe-shaped mask defines a third area III; depositing a first conductive film layer on the semiconductor layer along a first direction, a second thickness of the first conductive film layer equals D, a first angle between the first direction and a thickness direction of the first stripe-shaped mask and the second stripe-shaped mask equals a first angle θ₁, θ₁<tan⁻¹(L/H); depositing a second conductive film layer on the semiconductor layer along a second direction, a second angle between the second direction and the thickness direction of the first stripe-shaped mask and the second stripe-shaped mask equals a second angle θ₂, θ₂<tan⁻¹[L/(H+D)], 0<Htanθ₁+(H+D)tanθ₂−L<10 nm, the entire second area is covered by the first conductive film layer and the second conductive film layer, an interval area between the first conductive film layer and the second conductive film layer is formed on the third area and forms a nanoscale channel, the first conductive film layer located on the third area forms a source electrode, the second conductive film layer located on the third area forms a drain electrode.
 2. The method as claimed in claim 1, wherein the first thickness H is in a range of 200 nanometers to 400 nanometers.
 3. The method as claimed in claim 1, wherein the spacing distance L is in a range of 200 nanometers to 450 nanometers.
 4. The method as claimed in claim 1, wherein a first angle θ₁ is less than or equal to 45 degrees.
 5. The method as claimed in claim 1, wherein the second angle θ₂ is less than or equal to 45 degrees.
 6. The method as claimed in claim 1, wherein an extending direction of the first stripe-shaped mask and the second stripe-shaped mask is perpendicular to both the first direction and the second direction.
 7. The method as claimed in claim 1, further comprising removing the first stripe-shaped mask and the second stripe-shaped mask by a chemical reagent.
 8. The method as claimed in claim 7, wherein the first conductive film layer and the second conductive film layer are not free-standing structures, part of the first conductive film layer, that is located on the first area I and the second area II, is removed together with the first stripe-shaped mask and the second stripe-shaped mask, and part of the second conductive film layer, that is located on the first area I and the second area II, is removed together with the first stripe-shaped mask and the second stripe-shaped mask.
 9. The method as claimed in claim 7, wherein the first conductive film layer and the second conductive film layer are free-standing structures, part of the first conductive film layer, that is located on the first area I and the second area II, is removed by dry etching, and part of the second conductive film layer, that is located on the first area I and the second area II, is removed by dry etching.
 10. A method of making thin film transistor, comprising: forming a substrate; placing a first stripe-shaped mask and a second stripe-shaped mask on the substrate, wherein the first stripe-shaped mask and the second stripe-shaped mask are parallel, spaced from each other and have a same thickness, a first thickness of the first stripe-shaped mask and the second stripe-shaped mask equals H, a spacing distance between the first stripe-shaped mask and the second stripe-shaped mask equals L, top surfaces of the first stripe-shaped mask and the second stripe-shaped mask away from the substrate defines a first area I, side surfaces of the first stripe-shaped mask and the second stripe-shaped mask defines a second area II, an exposed surface of the substrate between the first stripe-shaped mask and the second stripe-shaped mask defines a third area III; depositing a first conductive film layer on the substrate along a first direction, a second thickness of the first conductive film layer equals D, a first angle between the first direction and a thickness direction of the first stripe-shaped mask and the second stripe-shaped mask equals a first angle θ₁, θ₁<tan⁻¹(L/H); depositing a second conductive film layer on the substrate along a second direction, a second angle between the second direction and the thickness direction of the first stripe-shaped mask and the second stripe-shaped mask equals a second angle θ₂, θ₂<tan⁻¹[L/(H+D)], 0<Htanθ₁+(H+D)tanθ₂−L<10 nm, the entire second area is covered by the first conductive film layer and the second conductive film layer, an interval area between the first conductive film layer and the second conductive film layer is formed on the third area and forms a nanoscale channel, the first conductive film layer located on the third area forms a source electrode, the second conductive film layer located on the third area forms a drain electrode.
 11. The method as claimed in claim 10, wherein the thickness of H is in a range of 200 nanometers to 400 nanometers.
 12. The method as claimed in claim 10, wherein the spacing distance is in a range of 200 nanometers to 450 nanometers.
 13. The method as claimed in claim 10, wherein the first angle θ₁ is less than or equal to 45 degrees.
 14. The method as claimed in claim 10, wherein a second angle θ₂ is less than or equal to 45 degrees.
 15. The method as claimed in claim 10, wherein an extending direction of the first stripe-shaped mask and the second stripe-shaped mask is perpendicular to both the first direction and the second direction.
 16. The method as claimed in claim 10, further comprising removing the first stripe-shaped mask and the second stripe-shaped mask by chemical reagent. 